Manufacture of metal carbonyls



Patented Sept. 13, l fifi MANUFACTURE OF METAL CARBONYLS Harold E. Podall and Hymin Shapiro, Baton Rouge, La., assignors to Ethyl Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Apr. 25, 1960, Ser. No. 24,256 3 Claims. (Cl. 23-203) This invention relates to metal carbonyls, particularly the manufacture of the transition metal carbonyls.

Some procedures for the preparation of certain metal carbonyls have been described in the literature. With particular metals, successful results are obtained by reacting the metal with carbon monoxide at high temperatures and pressures or in certain instances reacting par ticular metal salts with hydrogen and then carbon monoxide. These procedures are applicable only in limited instances, as, for example, with the metals nickel and iron. They likewise leave much to be desired since stringent process techniques are required and the metal or metal compound must be in particular form.

The procedures likewise are not available to the more diflicultly produced metal carbonyls. The most satisfactory procedure devised as yet for the preparation of certain more difiicultly produced metal carbonyls involves the reaction of their salts with a Grignard reagent and then reacting the product soaproduced with carbon monoxide. This two-step procedure has been improved by judicious choice of the Grignard reagent employed. However, even with these improvements the process suffers particular disadvantageswhich are to be overcome. For example, for some unexplained reason the process is relatively independent of variables such as pressure beyond a certain point. change is obtained in the rate of reaction or the yield when these variables are changed. Another inherent disadvantage in the process is that the yields are such that commercial employment of the procedure is not practical. A still further disadvantage is that, during the course or" reaction, byproduct metal, that is the metal desired to form the metal carbonyl compound, is obtained and this material cannot be converted to the desired carbonyl compound.

Accordingly, it is an object of this invention to provide a new and novel process for the preparation of transition metal carbonyls. A particular object is to provide a procedure whereby these materials, especially such compounds diflicultly obtainable by the prior art techniques, are obtained in higher yield than heretofore available. A specific object is to provide the carbonyls of the VI-B elements of the periodic chart of the elements in higher yield than heretofore obtainable.

The above and other objects of this invention are achieved by reacting a salt of a. transition metal of the 'B-series of group VI of the periodic chart of the ele- 'ments, including their oxides or sulfides, with a stable organomet-allic compound of a group II-B element of the periodic chart of the elements and carbon monoxide. The periodic chart of elements referred to above and hereinafter corresponds to the given on pages 392 and 393 of the Handbook of Chemistry and Physics, 36th edition (1954-1955), Chemical Rubber Publishing "Company. While the benefits of this invention are generally applicable to the salts of all transition metals of :group VI-B, the process is particularly well suited to the In other words, essentially no metals, molybdenum and tungsten. Further particular advantage is achieved when the organometallic compound is a compound of zinc. Thus, one embodiment of this invention comprises the reaction of a salt of a VI-B element with an organozinc compound, particularly alkyl- Zinc compounds, and carbon monoxide.

When employing the procedure of this invention, simultaneous reaction of the metal salt, the stable org'anometallic compound and the carbon monoxide is obtained thus providing an enhancementin yield, faster reaction rates and minimization of undesirable byproduct metal. Among further benefits of the process of this invention, it is generally applicable to all the designated transition metal salts producing such metals in chemical combination with carbon monoxide in higher yields than heretofore obtainable and with faster reaction rates. Thus, compounds which previously have not been obtainable or were produced in low yields by the prior art techniques are now provided in high yields, suitable for commercialization. It will be noted that the stringent processing operations of the prior art techniques are not required and the difliculty of producing by-product metal is overcome. For example, in the prior technique employing Grignard reagents, at the completion of the reaction, it is necessary to quench with Water to obtain the product. This operation is not required in the present process since the product is directly obtained from the reaction. Another particular advantage of the present process is that many varied compounds of the transition metals can be employed. In contrast, with certain metals and employing the Grignard technique, only certain valence states of the metal can be utilized. For example, in the case of the chromium, molybdenum, and tungsten carbonyl preparations only the trivalent, pentavalent, and hexavalent states respectively produce by far the best results. Still further advantages of the process of this invention will be evident as the discussion proceeds.

The salts of the transition metals employable are many and varied. For the purposes herein, the oxides and sulfides of these metals are also intended in the terminology salts although such are not truly salts. The transition metals include the metals of group VIB, of the periodic chart of the elements (Fisher Scientific Company). The salts of such metals include both inorganic and organic salts. Typical examples of the inorganic salts are the halides, phosphates, sulfites, sulfates, nitrates, fluosilicates, carbonates, oxides, sulfides, and the like salts of such metals. The organic salts of these metals include, for example, the carboxylates, e.g., alkyl, aryl, cycloalkyl, and the like, the alcoholates, e.g. phenates, alkoxides, and enolates and the thioalcoholates or mercaptides. Among the inorganic salts employable in the process of this invention are chromium bromide, iodide, fluoride and chloride, chromium carbonate, the various chromium oxides, chromium phosphate, chromium fluosilicate, chromium sulfate, chromium sulfide, chromium sulfite, and the like, including similar such compounds wherein chromium is replaced by the metals, molybdenum and tungsten. Among the organic salts of the transition metals employable in the process of this invention are included, for example, chromium acetate, chromium benzoate, chromium citrate, chromium formate, chromium lactate, chromium oxalate, chromium malonate, chromium valerate, chromium naphthenate, chromium oleate, chromium acetylacetonate, chromium toluate, chromium phenate, chromium ethylate, chromium decanoate, chromium thiornethylate, and the like salts of the transition metals described previously. It is to be understood that all Valence states of the metals are intended. For example, chromium is meant to denote both the chromic and chromous salts. In general, in the organic type salts, the organo portion will contain between 1 to 25 carbon atoms in each radical although higher such acid salts can be employed.

Such salts of the metals chromium, molybdenum and tungsten are preferred in the process because of their greater reactivity and economy. The process of this invention is especially well suited to the production of carbonyls of the metals molybdenum and tungsten which exhibit different problems and are more diflicult to prepare. Therefore, the salts of these metals are especially preferred. Although the carbonyl compounds of tungsten and molybdenum have heretofore been obtained only in low yields, according to the present process, they are readily obtainable in high yield.

For best results the inorganic salts of the transition metals, particularly the halides, are especially preferred. In those instances wherein the metal salt is a solid in the reaction mixture, it is generally desirable to employ such materials in finely divided form of the order of about 1,000 microns or less.

The organometallic compound employed in the process is one of'an element of the group II-B elements of the periodic table. Such elements include zinc, cadmium and mercury. Thev organo'rnetallic compound will usually contain between about 1 to 25 carbon atoms in ach organic radical, In general, themetal is attached to at least one carbon atom of an organic radical. It can additionally, however, be attached to other elements, as for example, the halides, hydrogen or another metal, particularly the group I-A metals. Typical examples of the group II-B organometallic compounds include the following: diisopropylzinc, diethylzinc, dimethylzinc, dibutylzinc, diamylzinc, diheXylzinc, dioctylzinc, methylethylzinc, ethyl-n-propyl zinc, isopropyl-n-butylzinc, nheptyl-n-octylzinc, ethylzinc bromide, ethylzinc chloride, ethylzinc iodide, n-buty-lzinc bromide, ethylzinc hydride,

' n-butylzinc hydride, dicyclohexylzinc, sodium Zinc triethyl, diphenylzinc, dibenzylzinc, and the like compounds of cadmium and mercury, such as diethyl cadmium, diethyl mercury, ethyl cadmium chloride, ethyl mercury iodide, diphenyl cadmium, dibenzyl mercury and the like.

For practical purposes and best results, the alkylzinc compounds are preferably employed. These compounds are more stable, more readily available and are of higher reactivity. Generally, each alkyl group therein will contain from 1 up to and including about 8 carbon atoms.

In general, the process is readily performed by adding the transition metal salt and the organometallic compound into a reaction vessel and pressurizing with carbon monoxide. If desired, the reaction can be conducted in the presence of an essentially inert liquid medium. The reaction mixture is usually agitated to provide adequate contact. In most instances the simultaneous reaction of these materials will take place at room temperature although heating is preferred to effect greater reaction rates. At the completion of the reaction the transition metal carbonyl is recovered in a conventional manner such as distillation, sublimation, or separation of the by-product leaving the product in the liquid medium, when employed, which can then be, recovered by concentration and filtration.

The process of this invention will be more fully understood by reference to the following examples. In all examples the parts and yields are by weight.

amp e I To a reactor equipped with external heating means, internal agitation, and means for maintaining pressure is added 1.0 parts of chromium trioxide, 5.0 parts of diethylzinc in 30. parts of diethyl ether under an inert atmosphere of nitrogen. The reactor is: then pressurized with 2,500 p.s.i.g. of carbon monoxide and heated with continuous agitation to 100 C. These conditions are maintained for a period of 4 hours. At the end of this Period, aftter cooling to room temperature, the gases i .4 the reactor are vented to the atmosphere and the mixture is quenched with water and dilute hydrochloric acid. The mixture is then extracted with diethyl ether and the ether layer separated and dried. The dry ether layer is subjected to distillation to concentrate the product. The concentrated liquor is then cooled in an ice bath and the chromium hexacarbonyl is filtered therefrom.

When this run is repeated employing a carbon monoxide pressure of 500 psi and a reaction time of 12 hours, similar results are obtained,

Example 11 The procedure of Example I is repeated with the exceptionthat 2.0 parts of molybdenum trichloride are reacted with 5.0 parts of diethyl zinc in 25 parts of tetrahydrofuran at a temperature of 120 C. for 3 hours with the pressure of the carbon monoxide at 1500 p.s.i.g. Molybdenumhexacarbonyl is obtained in high yield.

Example III When h ove mple i epeated mpl ying Parts of m yb en m tr oxid in. p ce of mo ybdenum trichloride, molybdenum hexacarbonyl is again obtained in high yield.

Example I V Tungsten hexacarbonyl is obtained when the procedure of Example II is repeated employing 2.3 parts of tungsten trioxide in place of the molybdenum trichloride.

Example V Employing the procedure of Example I, 1.6 parts .of chromic' chloride are reacted with 7.4 parts of diethyl zinc in 25 parts of diethyl ether at 100 C. for 4 hours and at a carbon monoxide pressure of 5000 p.s.i.g. Chro= mium hexacarbonyl is recovered as in Example I in high yield.

Example VI Employing the procedure of Example I molybdenum hexac arbonyl dimer is recovered in high purity and yield when 2.7 parts of molybdenum pentachloride are reacted with 8.8 parts of diphenylzinc in 30 par s of diethyl ether at 4000 p.s.i.g. pressure of carbon monoxide for 8 hours at 100 C.

Example VII n this r n 2.5 pa of r m u a ety a etona e a e e ed w t 5 p r o iethylz n in 2 parts of dioxane at a Pressure o 0 Ps -g o carbon m nox de and a temperature of 100 C. for 3 hours. Chromium hexan carbonyl is obtained in high yield.

Example VIII Employing the procedure of Example I, chrornic ace tate, dibenzylcadmium and carbon monoxide at a pressure of 15,000 p.s.i.g. are reacted in the dimethyl ether of diethylene glycol at 100 C. for 8 hours to produce chromium hexacarbonyl.

Example IX of molybdenum trichloride are reacted with 7.6 parts of di-n-propylzinc at a pressure of 7:500 p.s.i.g. of carbon monoxide in the presence of 30 parts. of toluene for 11 I hour at E a p e XI When tungsten hexachloride is reacted with diethyl mercury and carbon monoxide according to the procedure of Example I, tungsten hexacarbonyl is obtained.

Similar results are obtained when other group transition metals salts are employed in the above examples. For example, chromium sulfide and the like can be substituted for the salts employed above. For the organometallic compounds employed in the above examples one can substitute dimethylzinc, ethyl zinc bromide, ethyl zinc hydride, dibenzylzinc, sodium zinc triethyl, diethyl cadmium, dicyclohexyl cadmium, diphenyl mercury, and the like.

The temperature at which the reaction is conducted is not critical and generally temperatures between to about 200 C. are employed. In general, the higher the temperature the faster the reaction rate. Accordingly, for such purposes it is preferred to operate at temperatures ranging from 75 to 175 C., depending upon the reactants employed. Likewise, the pressure can be varied over a wide range from superatmospheric to subatmospheric pressures. Ordinarily, since the carbon monoxide is a gas, pressures above atmospheric are employed. A preferred range is between 500 to 4000 p.s.i.g. in order to obtain optimum results.

The time of reaction will likewise depend somewhat upon the other conditions under which the reaction is conducted although times between about 1 minute to 20 hours are generally quite adequate. In order to minimize side effects it is preferred to conduct the reaction for a period of from 5 minutes to 6 hours.

The proportions of the reactants can likewise be varied and generally are based upon the metal salt. In this connection between about 1 mole to 6 moles and higher of the organometallic compound are employed per mole of the metal salt. However, as the temperature is increased the number of moles of organometallic compound generally can be decreased. Where excesses of the organometallic compound are employed, such excesses may be recovered and reused. The carbon monoxide is generally employed in stoichiometric amounts, although excesses can be beneficially employed.

While the above examples indicate that an organic diluent is employed, it is to be understood that such are not essential. In general, when such are employed they should be essentially inert to the reactants. Furthermore, it is desirable, but not necessary, that they exhibit solubility for one or all of the reactants. Among such organic diluents which can be employed are included the hydrocarbons, ethers and amines. Among the hydrocarbons included are, for example, nonanes, octadecanes, hexanes, toluene, benzene, xylene, mesitylene and mixed hydrocarbons such as gasoline, diesel oil and the like petroleum fractions. Among the ethers employable are included, for example, the non-aromatics, aromatics and polyethers including for example, di-sec-butyl ether, di-nheptyl ether, diisopropyl ether, ethyl-isoamyl ether, methyl phenyl ether (anisole), p-tolyl ether, ethylphenyl ether, tetraethylene glycol dimethyl ether, and the dimethyl, diethyl, and di-n-butyl ethers of diethylene glycol. Among the amines which are employable are included dimethyl amine, diethyl amine, dioctyl amine, diphenyl amine, dicyclohexyl amine, methylethyl amine, p-methyl pyridine, o-methyl pyridine, 2,6-dimethyl pyridine, isoquinoline, trimethyl amine, tn'ethyl amine, tributyl amine, tricyclohexyl amine, and the like.

The coordinating solvents, especially the ethers, are particularly preferred since these materials exhibit a reaction promoting eifect.

The process provides products which are of considerable use. These products can be, for example, subjected to high temperatures, thereby providing decomposition to obtain the respective metals in finely divided form. For example, when molybdenum carbonyl is heated at a temperature above 250 C. in an inert atmosphere, 2. finely divided pyrophoric product is obtained which is useful in electronic tubes for anodes and support members or in alloying in making steels. Another particular use for the compounds produced according to the process of this invention is as additives to fuels for internal combustion engines and the like. For example, when sufficient chromium hexacarbonyl is added to commercial gasoline to obtain compositions containing 1 gram of chromium per gallon, the octane number of the gasoline is increased. The products are also useful as chemical intermediates in preparing organometallic compounds. These and other uses will be evident to those skilled in the art.

This application is a continuation-in-part of our copending application Serial No. 704,295, filed December 23, 1957, now abandoned.

Having thus described the process of this invention it is not intended that it be limited except as set forth in the following claims.

We claim:

1. The process for the manufacture of a group VI-B metal hexacarbonyl comprising reacting a salt of a transition metal of group VI-B of the periodic chart of elements with a stable diorganometallic compound of a group lI-B element and carbon monoxide at a temperature of 0200 C., said carbon monoxide being maintained at a pressure above atmospheric and up to about 10,000 p.s.i.g., said diorganometallic compound having its metal atom bonded directly to a carbon of each of the two organo groups.

2. The process of claim 1 wherein the diorganometallic compound is Zinc diethyl.

3. The process for producing a group VI-B metal hexacarbonyl comprising reacting a salt of a transition metal of group VI-B of the periodic chart of elements with a dialkyl zinc compound and carbon monoxide at a temperature of 0-200" 'C., said carbon monoxide being maintained at a pressure above atmospheric and up to about 10,000 p.s.i.g.

References Cited in the file of this patent UNITED STATES PATENTS 2,739,169 Hagemeyer Mar. 20, 1956 FOREIGN PATENTS 678,712 Great Britain Sept. 10, 1952 OTHER REFERENCES Sidgwick: Chemical Elements and Their Compounds, 1950, vol. 1, p. 415.

Babor et al.: General College Chemistry, 1940, p. 88. 

1. THE PROCESS FOR THE MANUFACTURE OF A GROUP VI-B METAL HEXACARBONYL COMPRISING REACTING A SALT OF A TRANSITION METAL OF GROUP VI-B OF THE PERIODIC CHART OF ELEMENTS WITH A STABLE DIORGANOMETALLIC COMPOUND OF A GROUP II-B ELEMENT AND CARBON MONOXIDE AT A TEMPERATURE OF 0-200*C., SAID CARBON MONOXIDE BEING MAINTAINED AT A PRESSURE ABOVE ATMOSPHERIC AND UP TO ABOUT 10,000 P.S.I.G., SAID DIORGANOMETALLIC COMPOUND HAVING ITS METAL ATOM BONDED DIRECTLY TO A CARBON OF EACH OF THE TWO ORGANO GROUPS. 